Stop Hotlinking of a document

New to this and need your help. I need to stop hotlinking of a document on a website hosted on a windows server 2003 IIS 6.0. I have tried .htaccess, free ISAPI, free Helicon etc. etc and I for the love of god can't figure it out. I'm new to scripting and would
very much appreciate any help.

I followed this guide but when I restarted IIS the ISAPI filter displayed status as not loaded and the arrow was red. I tried few times but same issue.